Preparation method of Ru-CeO2 single-atom catalyst for photothermal methane dry reforming with variable coordination

Abstract

This invention discloses a method for preparing a Ru-CeO2 single-atom catalyst for photothermal methane dry reforming with variable coordination, comprising the following steps: 1) preparing a Ru-CeO2 precursor based on a hydrothermal method; 2) preparing a Ru-CeO2 single-atom catalyst for photothermal methane dry reforming with variable coordination based on the Ru-CeO2 precursor. The catalyst prepared by this method has a high utilization rate of active metal and a low preparation cost.

Description

Technical Field

[0001] This invention belongs to the field of solar photothermal chemical conversion technology, and relates to a method for preparing a Ru-CeO2 single-atom catalyst for photothermal methane dry reforming with variable coordination. Background Technology

[0002] Converting two greenhouse gases into syngas using methane dry reforming is a promising, clean, and efficient technological route. The product can also be used as a raw material to produce other high-value-added chemicals. In nature, solar energy, as a clean energy source with large reserves, easy access, and wide distribution, has attracted widespread attention. However, its further large-scale application is limited by its low energy density and large intermittent fluctuations. Utilizing solar energy to drive methane dry reforming, and using solar chemical conversion technology to convert it into chemical energy with high energy density that is easy to store and transport, has attracted widespread attention. However, due to thermodynamic limitations such as high endothermic reaction and high activation energy, the reaction requires high temperatures to be driven. At these temperatures, the requirements for catalyst and reactor materials will be further increased. Therefore, it is feasible to use photothermal synergistic catalysis technology, which requires only lower temperatures to achieve a specified conversion rate / product yield. The principle is to utilize the photoelectron coupling of the catalytic thermal active centers generated by the photothermal catalyst under illumination, synergistically increasing the syngas yield. However, in existing research, the utilization rate of active metals by photothermal catalysts is low, which will further increase the catalyst preparation cost. Therefore, introducing single-atom catalysis on the basis of photothermal catalysis to achieve near 100% utilization while enhancing reactant dissociation is an ideal strategy. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a Ru-CeO2 single-atom catalyst for photothermal methane dry reforming with variable coordination. The catalyst prepared by this method has a high utilization rate of active metal and a low preparation cost.

[0004] To achieve the above objectives, this invention discloses a method for preparing a Ru-CeO2 single-atom catalyst for photothermal methane dry reforming with variable coordination, comprising the following steps:

[0005] 1) Preparation of Ru-CeO2 precursor based on hydrothermal method;

[0006] 2) Prepare a Ru-CeO2 single-atom catalyst for photothermal methane dry reforming based on the Ru-CeO2 precursor.

[0007] The specific operation of step 1) is as follows:

[0008] Cerium nitrate hexahydrate and ruthenium nitrite nitrate were dissolved in ultrapure water to obtain solution A; sodium hydroxide was dissolved in ultrapure water to obtain solution B. Solution A was added dropwise to solution B, and the mixture was stirred at room temperature. Then, a hydrothermal reaction was carried out to obtain the Ru-CeO2 catalyst precursor.

[0009] The temperature during the hydrothermal reaction is 100℃.

[0010] The operation process of step 1) is as follows:

[0011] 2.17 g of cerium nitrate hexahydrate and 13.7 mg of ruthenium nitrite nitrate were dissolved in 10 mL of ultrapure water to obtain solution A; 24 g of sodium hydroxide was dissolved in 90 mL of ultrapure water to obtain solution B. Solution A was added dropwise to solution B, and the mixture was stirred at room temperature for 30 min. Then, it was placed in a hydrothermal reaction at 100 °C to obtain the Ru-CeO2 catalyst precursor.

[0012] The operation process for step 2) is as follows:

[0013] The Ru-CeO2 catalyst precursor was separated into a supernatant and a precipitate. The precipitate was washed, dried, and then calcined to obtain a Ru-CeO2 single-atom catalyst for photothermal methane dry reforming with variable coordination.

[0014] The Ru-CeO2 catalyst precursor was separated into supernatant and precipitate by centrifugation.

[0015] The process of washing the precipitate is as follows:

[0016] The precipitate was washed with ultrapure water and anhydrous ethanol until the pH of the supernatant was 7.

[0017] The process of calcining the precipitate is as follows: the precipitate is heated to 400°C at a rate of 5°C / min and calcined for 4 hours.

[0018] By controlling the hydrothermal reaction time, different catalyst coordination environments can be obtained, thereby enabling targeted regulation of catalytic selectivity and stability.

[0019] The present invention has the following beneficial effects:

[0020] The method for preparing the photothermal methane dry reforming variable coordination Ru-CeO2 single-atom catalyst of the present invention involves anchoring Ru single-atom sites on a CeO2 semiconductor support via a co-hydrothermal method. Utilizing the oxygen vacancies generated by the strong metal-support interaction between Ru and the CeO2 support, which can be controlled during the preparation process, and the Ru sites at the single-atom scale, rapid and effective activation and dissociation of the CO2 / CH4 feed gas is achieved. Furthermore, the semiconductor effect of the CeO2 support is utilized to induce photoelectrons under illumination, which are then transferred to the catalyst surface to further accelerate the activation of the feed gas molecules. This method has a low preparation cost. In addition, the plasmon resonance effect induced by the Ru sites attached to the CeO2 surface increases the local surface temperature, enhancing the reaction at the active sites and achieving higher reactivity while reducing manufacturing costs. Attached Figure Description

[0021] Figure 1 The image shows the transmission electron microscopy (HAADF) characterization of the Ru-CeO2 single-atom catalyst in Example 1.

[0022] Figure 2 This is a schematic diagram of the CO / H2 generation rate activity of Ru-CeO2 single-atom catalysts with different coordination environments under photothermal catalysis conditions in Example 1. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion regarding the concepts disclosed in the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0024] The accompanying drawings show structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not drawn to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0025] Example 1

[0026] The preparation method of the photothermal methane dry reforming variable coordination Ru-CeO2 single-atom catalyst of the present invention includes the following steps:

[0027] 1) Preparation of Ru-CeO2 precursor: 2.17 g of cerium nitrate hexahydrate and 13.7 mg of ruthenium nitrite nitrate were dissolved in 10 mL of ultrapure water to obtain solution A; 24 g of sodium hydroxide was dissolved in 90 mL of ultrapure water to obtain solution B. Solution A was slowly added dropwise to solution B, and the mixture was stirred at room temperature for 30 min. Then, it was subjected to hydrothermal reaction at 100 °C to obtain Ru-CeO2 catalyst precursor.

[0028] 2) Preparation of Ru-CeO2 catalyst: The Ru-CeO2 catalyst precursor was separated into supernatant and precipitate by centrifugation. The precipitate was washed with ultrapure water and anhydrous ethanol until the pH of the supernatant was 7. The precipitate was then dried at 80℃ for 12 h, followed by calcination at 400℃ for 4 h at a rate of 5℃ / min to obtain the Ru-CeO2 catalyst. Subsequently, it was reduced with hydrogen at 500℃ and 80 mL / min for 7 min to obtain the Ru-CeO2 single-atom catalyst, which was then used for subsequent photothermal catalytic dry reforming of methane to syngas activity testing. Characterization was performed using 9790-II type chromatography, and the detection results are as follows: Figure 1 and Figure 2 As shown.

[0029] It should be noted that this invention anchors Ru single-atom sites on a CeO2 semiconductor support via a co-hydrothermal method. Utilizing the oxygen vacancies generated by the strong metal-support interaction between Ru and the CeO2 support, which can be controlled during the preparation process, and the Ru sites at the single-atom scale, rapid and effective activation and dissociation of the CO2 / CH4 feedstock gas is achieved. Furthermore, the semiconductor effect of the CeO2 support allows for photoelectric effect under illumination, exciting photoelectrons that transfer to the catalyst surface, further accelerating the activation of the feedstock gas molecules. In addition, the Ru sites attached to the CeO2 surface induce a plasmon resonance effect, increasing the local surface temperature and enhancing the reaction at the active sites. Through the coupled thermocatalytic and photo-initiated effects, including the photoelectric effect and plasmon resonance effect, high reactivity is achieved. During the preparation process, the single-atom coordination environment is controlled by hydrothermal time-directed regulation, thereby controlling product distribution and catalytic stability, achieving highly efficient photothermal catalytic dry reforming of methane to syngas. The design strategy of this catalyst not only makes full use of the traditional thermocatalytic active centers, but also simultaneously couples the photoelectric effect, the thermocatalytic effect, and the plasmon resonance effect. This multi-effect coupling significantly improves the syngas yield. In addition, the introduction of single-atom sites during the preparation process greatly increases the surface energy of the catalyst and lowers the dissociation energy barrier of the reactants.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. Use of a variable coordination Ru-CeO2 monatomic catalyst in the photo-thermal methane dry reforming to produce carbon monoxide and hydrogen, characterized in that, The preparation method of the Ru-CeO2 single-atom catalyst comprises the following steps: 2.17 g of cerous nitrate hexahydrate and 13.7 mg of ruthenium nitrosyl nitrate are dissolved in 10 mL of ultrapure water to obtain an A solution; 24 g of sodium hydroxide is dissolved in 90 mL of ultrapure water to obtain a B solution, the A solution is added dropwise into the B solution, and then stirred at room temperature for 30 min, and then subjected to a hydrothermal reaction at 100 DEG C to obtain a Ru-CeO2 catalyst precursor; The Ru-CeO2 catalyst precursor is separated into supernatant and precipitate, the precipitate is washed, and then the precipitate is dried, followed by calcining the precipitate to obtain a Ru-CeO2 single-atom catalyst for photo-thermal dry reforming of methane; The process of calcining the precipitate is that the precipitate is calcined at a speed of 5 DEG C / min to 400 DEG C for 4 h.

2. Use according to claim 1, characterized in that, The Ru-CeO2 catalyst precursor is separated into supernatant and precipitate by using a centrifugal method.

3. Use according to claim 1, characterized in that, The process of washing the precipitate is that: The precipitate is washed with ultrapure water and anhydrous ethanol until the pH value of the supernatant is 7.

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